This invention relates to a method of separating RDX (cyclotrimethylene tetranitramine) and HMX (cyclotetramethylene tetranitramine) using a double cosolvent system.
RDX and HMX can be coproduced by a modified Bachmann reaction [Bachmann et al., J. Am. Chem. Soc., 71, 1842 (1979)] i.e. by the reaction of methenamine, ammonium nitrate and acetic anhydride. The resulting product can contain a 70/30 RDX/HMX by weight mixture. This process is more economical than Bachmann batch processes which produce very little HMX. In order to take advantage of the more economical production of RDX and HMX using the modified Bachmann process, it is necessary to develop a means to separate the RDX and HMX components as essentially pure products from the reaction mixture.